Irakli Simonia

Frozen Hydrocarbons in Comets

Recent investigations of the luminescence of frozen hydrocarbon particles of icy cometary halos have been carried out. The process of luminescence of organic icy particles in a short-wavelength solar radiation field is considered. A comparative analysis of observed and laboratory data leads to 72 luminescent emission lines in the spectrum of the comet 153P/Ikeya-Zhang. The concept of cometary relict matter is presented, and the creation of a database of unidentified cometary emission lines is proposed.

Unidentified Cometary Emission Lines as the Photoluminescence of Frozen Hydrocarbon Particles

We discuss the possible nature of unidentified cometary emission lines. We propose a model of the ice particles in cometary halos as a mixture of frozen polycyclic aromatic hydrocarbons (PAHs) and acyclic hydrocarbons. We describe the general properties of frozen hydrocarbon particles (FHPs) and suggest interpreting some of the unidentified cometary emission lines as the photoluminescence of FHPs. We compare the positions of unidentified emission lines in the spectrum of Comet 122P/de Vico with the positions of quasi-lines in the photoluminescence spectrum of PAHs that were dissolved in acyclic hydrocarbons at a temperature of 77 K and that constituted a polycrystalline solution. We estimate the detectability of FHP photoluminescence in cometary spectra.

Cathodoluminescence Microscopy and Spectroscopy of Micro- and Nanodiamonds: An Implication for Laboratory Astrophysics

Color centers in selected micro- and nanodiamond samples were investigated by cathodoluminescence (CL) microscopy and spectroscopy at 298 K [room temperature (RT)] and 77 K [liquid-nitrogen temperature (LNT)] to assess the value of the technique for astrophysics. Nanodiamonds from meteorites were compared with synthetic diamonds made with different processes involving distinct synthesis mechanisms (chemical vapor deposition, static high pressure high temperature, detonation). A CL emission peak centered at around 540 nm at 77 K was observed in almost all of the selected diamond samples and is assigned to the dislocation defect with nitrogen atoms. Additional peaks were identified at 387 and 452 nm, which are related to the vacancy defect. In general, peak intensity at LNT at the samples was increased in comparison to RT. The results indicate a clear temperature-dependence of the spectroscopic properties of diamond. This suggests the method is a useful tool in laboratory astrophysics.

Frozen hydrocarbon particles of cometary halos as carriers of unidentified emissions

The possible nature of unidentified cometary emissions is under discussion. We propose a new model of the ice particles in cometary halos as a mixture of frozen polycyclic aromatic hydrocarbons and acyclic hydrocarbons. We describe principal properties of frozen hydrocarbon particles (FHPs) and suggest interpreting some of the unidentified cometary emission lines as the photoluminescence of FHPs. The results of comparative analysis are present.

Luminescence of Dust in the Nebula CED 201

This article is a study of luminescence in reflection nebulae and other objects consisting of dust or containing solid matter. New concepts and ideas, in particular the concept of frozen hydrocarbon particles, are proposed. Luminescence emission in the spectrum of the reflection nebula CED 201 is studied. Data analysis strategies and the identification process are discussed. Six previously unknown emission features are discovered in the spectrum of CED 201 over 4650-7525 Å. Three are identified as photoluminescence of solid hydrocarbons and the others are ascribed to ERE. It is proposed that the dust component of CED 201 be regarded as a complex of frozen hydrocarbon particles.

Photoluminescence and cathodoluminescence by cosmic dust

The photoluminescence and possible cathodoluminescence of cosmic dust is considered. It is shown that the dust of planetary nebulae can luminesce under the action of fluxes of charged particles. The results of a comparative analysis of unidentified emission features in the optical spectrum of the nebula NGC 7027 and the luminescence emission of a number of minerals is presented. It is shown that the dust in this nebula includes diamond grains.

Organic molecules of cometary substance

Unidentified emissions are observed in spectra of most comets. These separate lines and bands were not possible to be identified earlier by standard methods. A great number of narrow lines of unknown nature were tabulated [11]. For solving the problem of unidentified cometary emissions, had developed the theoretical model of frozen hydrocarbon particles of icy halos of comets and described the mechanism of FHPs photoluminescence [6]. The comparison of laboratory and observed data showed that hundreds of cometary emissions not identified earlier are the photoluminescence of frozen hydrocarbon particles. In [6] particularly suggested that the mixture of frozen polycyclic aromatic hydrocarbons and alkanes can be among the ices of cometary nuclei. These mixtures are the solid solutions of substance – solvent type; here the substance means polycyclic aromatic hydrocarbon (PAH), and the solvent – acyclic hydrocarbons. The optical properties of the solution are determined by the properties of a solvent, by the c...

Triton surface evolution

Recent physical data of the Triton surface characteristics are given, with particular reference being made to the factors determining the mechanisms of that satellites surface evolution. It is suggested that the photolysis, caused in Tritons ice surface by short-wave Solar radiation, should be considered as the basic mechanism responsible for the evolution of the surface of the satellite. Photodissociation of the CH 4 + h x M CH 3 +H-type is discussed. Ethane C 2 H 6 is shown to be the basic substance resulting from the above mentioned photodissociation and subsequent reaction involving CH 3 molecules. The time required for full photodestruction of CH 4 ice on Triton surface has been calculated, as well as the surface temperature of the satellite. Some other issues are touched upon.

The Legendary Fourth-Century Total Solar Eclipse in Georgia: Fact or Fantasy?

In the early fourth century AD, a sudden return of daylight after a darkening of the sky purportedly swayed King Mirian of Georgia to convert to Christianity. Medieval written sources and modern geophysical models suggest that Mirian, whilst on a mountain top near the city of Mtskheta, may have observed a total solar eclipse (TSE). Adjusting for both visibility corrections and constraints on the accumulated clock error known as ΔT, we examine the local circumstances of the TSE of AD 6 May 319, which Gigolashvili et al. (Astronomical and Astrophysical Transactions 26, 199–201, 2007; Transdisciplinarity in Science and Religion 6, 217–221, 2009) recently proposed as the most likely natural explanation. If the basis for the legendary accounts of Mirian’s conversion is this TSE—but we make no judgment upon this question—then the value of ΔT inferred from written sources agrees well with generally-accepted values, such as those derived by Morrison and Stephenson (Journal for the History of Astronomy 35, 327–336, 2004), namely, ΔT ≈ 7,450 ± 180 s. We also show the extent to which this TSE would have seemed remarkable to observers at Mirian’s presumed location and less so to those nearby at lower elevations.

On the nature of unidentified cometary emission lines

The nature of unidentified cometary emission lines is discussed. A model of ice particles in cometary halos as a mixture of frozen polycyclic aromatic hydrocarbons (PAHs) and acyclic hydrocarbons is considered. The properties of frozen hydrocarbon particles are described and 5–7% of the unidentified cometary emission lines are considered as the photoluminescence of frozen hydrocarbons. The positions of unidentified emission lines in the spectrum of Comet 19P/Borrelly are compared with the positions of quasi-lines in the photoluminescence spectra of PAHs that were dissolved in acyclic hydrocarbons at a temperature of 77 K and that constitute a polycrystalline solution.